Bit

Layer 0 (Bit)

The specification for the setup of a UART is:

• 8 data bits
• 2 start bits
• 1 stop bit
• No parity

This layer is typically implemented in hardware on a microcontroller, but could also be implemented using 'bit banging' in software. The baud rate is not part of the specification and is set by the system designer.

There are no inter-byte timing requirements: bytes can be transmitted with large time gaps between them or back-to-back.